I want to know if it is possible to measure solar irradiance with a light dependent resistor. I know the ldr measures light intensity. Can it be somehow coded on Arduino so that it gives a good approximation of the solar irradiance? It does not need to be accurate, just close.
Perhaps, but it depends on how you define "close" and "solar irradiance". LDRs see only a certain range of wavelengths, with variable efficiency, and some types aren't even sensitive to visible light.
You would need a commercial quality solar irradiance meter to compare and calibrate your LDR over a wide range of light levels and conditions.
Hi.
Not about LDR, but days ago I found this article about using a phototransistor.
If you are serious about measuring solar irradiance, here is a great site for DIY construction of inexpensive, but high quality solar radiation monitoring equipment.